Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Conventional optical lenses can create images by capturing the light waves emitted by an object and then bending them. However, objects may also emit “evanescent” waves containing a lot of information at very small scales that can be much harder to measure. This is because the evanescent waves decay exponentially and thus may never reach the image plane—a threshold in optics known as the diffraction limit.
The diffraction limit can prevent resolving two objects closer than half the wavelength of light using lens-based far-field optics. For a finer optical resolution, one usually employs a lensing effect by surface-plasmon excitation or fluorescence microscopy involving molecular excitations. Until very recently, the only practical way to see sub-diffraction limited features was by using a near-field optical microscope which can capture evanescent waves using a nanosized mechanical tip.
In recent years there have been various efforts to recover and project the evanescent waves into the far field. Metamaterials-based superlenses with properties such as negative refractive index offer one possible solution to overcome the diffraction limit. Use of spherical microlenses and nanolenses may offer new possibilities of lens-based near-field detection and high resolution optical imaging at low intensities. These lenses can be shown to provide lens-based near-field focusing in high resolution optical microscopy.
New types of self-assembled nanolenses that may overcome the diffraction limit of light are an exciting new area of research. Such nanolenses may allow features as small as 200 nm to be resolved. In biological systems there are several examples of arrays of miniaturized lenses such as insect's compound eyes. The present disclosure appreciates that miniature lenses (e.g., microlenses or nanolenses) can be adapted for use in a variety of optical devices like charge-coupled device (CCD), digital projectors and photovoltaics. Fabrication of such microlenses and/or nanolenses (i.e., hereinafter simply miniature lenses) can be carried out by a top-down approach using sophisticated tools like lithography, contact printing, inkjet printing, focused ion beam, and UV laser etc., where some examples may use a self-assembly process for fabricating a single lens. The present disclosure appreciates the possibilities associated with the use of miniature lenses, and thus identifies that there is a need for a commercially feasible method for fabricating such lenses.